JPH07156394A - Ink jet printer head - Google Patents

Abstract

PURPOSE:To provide an ink jet printer head in which ink can be rapidly supplied from an ink tank to an ink pressure chamber without sucking the air from a nozzle outlet to the chamber. CONSTITUTION:An ink pressure chamber 16 having a piezoelectric element 22 is formed in a printing head body 12, and ink in the chamber 16 is injected to a print sheet through a nozzle 14 and a nozzle outlet 20. Ink in an ink tank 18 is supplied to the chamber 16 through an ink supply passage 24. An electrode 28 is provided on an inner surface of the nozzle 14, and a voltage is applied to the chamber from a power source 32 at the time of supplying ink. Accordingly, ink containing an electric viscous fluid having a dye component such as carbon black, etc., is improved in its viscosity, thereby rapidly supplying the ink to the chamber without sucking the air from the outlet 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer head.

[0002]

2. Description of the Related Art Conventionally, an ink jet printer head of this type is shown in FIG. In this inkjet printer head, a voltage is applied to a piezo element 22 provided around the ink pressure chamber 16 to deform it, and the volume of the ink pressure chamber 16 is reduced to increase the pressure in the ink pressure chamber 16. By utilizing the pressure increase, the ink in the ink pressure chamber 16 is ejected through the nozzle 14 and the nozzle outlet 20 communicating with the ink pressure chamber 16. After that, the piezo element 22
When the shape of the piezo element 22 is restored by cutting off the voltage applied to the ink, the volume of the ink pressure chamber 16 returns to the volume before the ink ejection, and the pressure in the ink pressure chamber 16 also decreases. Then, due to the pressure difference between the ink tank 18 and the ink pressure chamber 16, the ink in the ink tank 18 passes through the ink supply passage 24 and the ink pressure chamber 16
Is supplied to.

However, during this ink supply, air is drawn into the ink pressure chamber 16 from the nozzle outlet 20 at the same time as the ink supply from the ink tank 18. Since this air becomes bubbles in the nozzle 14 or the ink pressure chamber 16, even if the pressure in the ink pressure chamber 16 is increased by deforming the piezo element 22 for ejecting ink after that, the pressure increase does not occur. The ink was not absorbed by the bubbles and could not be ejected without sufficient force being applied to the ink, resulting in poor print quality. In order to alleviate the above problem, a method has been adopted in which, when ink is supplied from the ink tank 18 to the ink pressure chamber 16, the ink supply passage 24 is enlarged to reduce the flow resistance of the ink.

[0004]

However, in the above method, the ink supply passage 2 due to the viscosity of the ink is used.
4 is effective when considering only the frictional resistance of No. 4, but when actually considering the continuity of the ink fluid, in the configuration shown in FIG.
In order to be sucked in, the upstream ink including the ink tank 18 must flow. Therefore, although the frictional resistance of the ink supply passage 24 is reduced,
The ink pressure chamber 16 is promptly affected by the inertial mass of the fluid.
Cannot be supplied with ink. This could not prevent the air from being drawn into the ink pressure chamber 16 from the nozzle outlet 20.

The present invention has been made to solve the above-mentioned problems, and when supplying ink into the ink pressure chamber, air is not drawn into the ink pressure chamber from the nozzle outlet, and the ink tank It is an object of the present invention to provide an inkjet printer head that can quickly supply ink to the ink pressure chamber.

[0006]

In order to achieve this object, an ink jet printer head of the present invention is used in an ink jet printer which ejects ink from an ejection nozzle by pressurizing the ink supplied into an ink pressure chamber. In the inkjet printer head, the ink is composed of an electrorheological fluid having a pigment component, and a pair of electrodes arranged in the vicinity of the connection portion between the ejection nozzle or the ink pressure chamber and the ejection nozzle, Means for applying a voltage to the electrodes during the operation of supplying the ink to the ink pressure chambers.

[0007]

In the ink jet printer head of the present invention having the above-mentioned structure, the ink having the pigment component composed of the electrorheological fluid changes in viscosity depending on the strength of the applied voltage or becomes jelly-like. Since a voltage is applied to the electrodes during the operation of supplying the ink to the ink pressure chamber, the viscosity of the ink located near the ejection nozzle increases. Therefore,
Air is less likely to be drawn into the ink pressure chamber from the ejection nozzle, and ink can be quickly supplied from the ink tank to the ink pressure chamber.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, in the ink jet printer head 10 of this embodiment, the print head body 1
An ink pressure chamber 16 that holds the ink to be ejected is formed inside 2, and a piezoelectric element 22 that is deformable by applying a voltage is formed on a part of the outer side surface of the ink pressure chamber 16. It is equipped. Further, the ink pressure chamber 16 communicates with the nozzle outlet 20 provided on the surface of the print head body 12 through the nozzle 14, so that the ink in the ink pressure chamber 16 is discharged from the nozzle 14 and the nozzle outlet 20. It is ejected to a print sheet (not shown) through the.

Further, the ink pressure chamber 16 is in communication with the ink tank 18 via the ink supply passage 24, and the ink stored in the ink tank 18 is stored in the ink pressure chamber 16 via the ink supply passage 24. Is supplied to. An electrode 28 is provided on the inner surface of the nozzle 14, and a high voltage (several hundreds of volts) is applied to the electrode 28 to apply an electric field. An electrorheological fluid having a pigment component such as carbon black is used as the ink. Here, the electrorheological fluid is a general term for colloidal solutions whose apparent viscosity can be changed by applying an electric field. The response speed at which the viscosity changes is very fast, 1 msec or less, and the range of viscosity change ranges from several centipoise to almost solid.

Next, the operation of the ink jet printer head 10 having the above-described structure during ink ejection and refill will be described with reference to FIG.

First, in the initial state shown in FIG. 2A, when a drive pulse is applied to the piezo element 22 by a power supply device (not shown), the piezo element 22 is deformed as shown in FIG. The volume of 16 is reduced. Since the pressure in the ink pressure chamber 16 rises accordingly,
Due to the pressure increase, the ink in the ink pressure chamber 16 is pushed out, ejected from the nozzle outlet 20 through the nozzle 14, and becomes an ink droplet 26 to reach on a print sheet (not shown).

Then, at the same time when the drive pulse applied to the piezo element 22 ends, a voltage of several hundred volts is applied to the electrode 28 provided on the inner surface of the nozzle 14. As a result, an electric field is applied to the ink in the nozzle 14, and the ink instantly becomes jelly-like. As shown in FIG. 2C, the piezo element 22
Returns to the shape before ejecting ink, the volume of the ink pressure chamber 16 is restored to the initial state shown in FIG. Along with this, the pressure in the ink pressure chamber 16 decreases. At this time, since the ink inside the nozzle 14 is jelly-shaped and has a large flow resistance, the ink does not flow toward the ink pressure chamber 16 due to this pressure reduction. Therefore, the amount of ink corresponding to the recovery volume up to the initial state is supplied from the ink tank 18 through the ink supply passage 24. As a result, the pressure in the ink pressure chamber 16 is restored, so that it is possible to prevent the ink from being sucked from the nozzle 14 and also to prevent the air from being drawn from the nozzle outlet 20.

Finally, as shown in FIG. 2D, the pressure in the ink pressure chamber 16 is recovered (returned to the shape before the piezo element 22 ejected ink), and at the same time, the voltage application to the electrode 28 is stopped. Then, the ink returns to the same viscosity characteristic as the ink in the ink pressure chamber 16, and the initial state before the ink ejection (see FIG.
The same state as (a)) is obtained. That is, by repeating the cycle shown in FIGS. 2A to 2D described above, continuous ejection can be realized without entraining bubbles in the ink pressure chamber 16.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope.

For example, although the electrode 28 is provided in the nozzle 14 in the above-described embodiment, the same effect as that in the above-described embodiment can be obtained even if the electrode 28 is provided in the vicinity of the connecting portion between the ink pressure chamber 16 and the nozzle 14.

[0017]

As is apparent from the above description, according to the ink jet printer head of the present invention, the electrode is provided in the nozzle and the voltage is applied to the electrode when the ink is supplied into the ink pressure chamber. It has become so.
Therefore, after ejecting the ink in the ink pressure chamber, the ink can be promptly supplied into the ink pressure chamber, and it is possible to reliably prevent the drawing of the air from the ejection nozzle, so that high quality printing is performed. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an example of an inkjet printer head embodying the present invention.

FIG. 2 is a cross-sectional view showing an ink jetting operation of the inkjet printer head of this embodiment.

FIG. 3 is a cross-sectional view showing a configuration of a conventional inkjet printer head.

[Explanation of symbols]

 10 Inkjet Printer Head 14 Nozzle 16 Ink Pressure Chamber 18 Ink Tank 22 Piezo Element 24 Ink Supply Passage 28 Electrode 32 Power Supply

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B41J 2/175 B41J 3/04 102 Z

Claims (1)

[Claims] 1. An inkjet printer head for use in an inkjet printer that ejects ink from an ejection nozzle by pressurizing the ink supplied to the ink pressure chamber, wherein the ink is composed of an electrorheological fluid having a pigment component. In addition, a pair of electrodes arranged in the vicinity of the connecting portion between the ejection nozzle or the ink pressure chamber and the ejection nozzle, and means for applying a voltage to the electrode during the operation of supplying ink to the ink pressure chamber. An inkjet printer head characterized by being provided.